Teaching

Job

Tutelages

Team 03: Histone variants and the nuclear envelope in heterochromatin organization

Our group is interested in the molecular mechanisms implicated in maintenance and developmental dynamics of heterochromatin organization in the model system Arabidopsis. We study heterochromatin composition in histone variants, heterochromatin position within the nucleus in respect to the nuclear envelope and the transcriptional regulation occurring at heterochromatic loci.

Research

Historically, our laboratory was one of the pioneers in the discovery of a specific class of repeated sequences in the Arabidopsis genome, the clusters of 5S ribosomal RNA (rRNA) genes that encode a critical RNA component of the ribosome. Despite being situated within the transcriptionally repressive environment of pericentromeric heterochromatin, part of the 5S rRNA genes is highly transcribed. Our work showed that 5S rRNA expression is controlled through the availability of its specific transcription factor TFIIIA, and epigenetic mechanisms such as the RNA directed DNA methylation pathway. Together, these different modes of regulation allow fine-tuning of 5S rRNA transcription during development and overcome the repressive effect of the heterochromatic environment.

While we continue studying 5S rDNA clusters as model genes situated within heterochromatin, we now concentrate our efforts on better defining intrinsic features of heterochromatin organization and its dynamics. For that purpose we pursue two complementary approaches, which aim to identify the critical players involved in establishment and maintenance of heterochromatin in Arabidopsis:

We study histone variants and their mode of incorporation into chromatin, which is controlled by specific histone chaperone proteins. Our aim is to understand how the different variants together with their specific post-translational modifications impact heterochromatin organization and function.

We further investigate the molecular structures implicated in the nuclear-cytoplasmic crosstalk and focus on identifying complexes that link chromatin to the nuclear periphery. Indeed, the periphery of the nucleus has emerged as an anchoring point for certain chromatin domains and to impact their expression. Using reverse genetic approaches and specifically developed 3D imaging tools in collaboration with bio-mathematicians, we aim to understand the interrelationship between nuclear position, chromatin organization and gene expression.